MARGARET WARNER: We begin with the power outage that has paralyzed much of the northeast United States and parts of Canada tonight. A short time ago New York City Mayor Michael Bloomberg held a news conference at City Hall to discuss the situation there.

MICHAEL BLOOMBERG, Mayor, New York City: For some reason or other, there was a power failure in northern New York or Southern Canada that cascaded down through the system and affected the power grid as far east as Connecticut, as far south as New Jersey, and as far west as Ohio.

To the best of our knowledge, nobody has been injured during the evacuation procedure from tall buildings or from the subways. There are people who are still in the subways as of last report but the police are saying that the evacuation procedures are working, people are calm, and that they are getting out. A lot of people are inconvenienced clearly. Most hospitals have power; one hospital does not, Downstate Hospital in Brooklyn.

The police commissioner and the fire commissioner and the commissioner of… deputy commissioner for Office of Emergency Management are all here, and what they report in summary is a very quiet city. There are no fires of any size going on at the moment.

There’s no criminal activity of any size taking place or hasn’t been reported; 911 is working; 311 is working. Things like traffic lights are not working. The police department has dispersed people to major intersections to try to help with traffic direction. The fire department and police department have called in all of their staff, those that had been on earlier and those that were scheduled to come on. So we are fully staffed.

Our advice to people is to be very careful in going home. It is very hot out there. The water supply is safe and you should drink a lot of water. You should keep your refrigerator doors closed. You should open your windows. It’s also important that you turn off all electrical appliances, particularly air conditioners, because as the power comes back, Con Ed and the other power companies will have a very difficult time if the demand is 100 percent.

MARGARET WARNER: For more, we turn to Matthew Wald, reporter for The New York Times, he joins us by phone; and Lawrence Makovich, senior director for North American Electric Power at Cambridge Energy Research Associates, an international energy consulting firm.

Welcome to you both. Matthew Wald, I don’t know if you’ll know the answer to this, but we just heard Mayor Bloomberg say — his latest information was this started in northern New York or southern Canada and cascaded down.

MATTHEW WALD: Right. That’s possible. At this time of year, we are usually importing electricity from Canada, and if the province of Ontario is in fact blacked out, it’s possible that something went wrong internal in Ontario. And when we lost supply, it set off a cascade in the United States. We’ll probably know that in a day or two, but that’s certainly possible.

MARGARET WARNER: And Mayor Bloomberg also suggested that, at some point, Con Edison for instance, the power company that actually supplies New York City, also then shuts things down, shuts power down itself.

MATTHEW WALD: Well, if they’re lucky. Since 1965 when we had a blackout all over the Northeast, we have evolved to a situation where we’re trying to prevent cascading blackouts. We’ve done pretty well. There was a big blackout in 1977, but it didn’t cover the whole Northeast.

And the way we survive these is, when the system starts to collapse, you cut off the area that has a problem so it doesn’t take down the whole house of cards. The essential problem is that the eastern interconnection all over North America east of the Rockies and north of Texas is very tightly linked together.

On a day like today, it’s, 90 degrees here, all the air conditioners are running, you get a failure somewhere and if the failure is big enough, it can cause a second failure. You lose a transmission line, you lose a generating station, and suddenly part of the system is overloaded and in a cascading fashion, more and more gets overloaded, and it just starts to fall down like a house of cards.

MARGARET WARNER: Lawrence Makovich, how do you explain this happening? This has not been the hottest summer by far in the northeast, I mean not at all. In fact, this is really the first or second week of serious heat. Isn’t the system set up to be much more redundant than this and to avoid this kind of thing?

LAWRENCE MAKOVICH: Yes, you make a good point. This hasn’t been a terribly hot summer, and usually a power system is highly stressed as you get towards the end of a week of a heat wave.

But as Matthew’s pointed out, this is… our electric supply comes from a very interdependent network. It is a network that typically operates with the redundancy that you asked about that’ll allow it to handle two or three major things going wrong. But if we get four or five things happening, we pass a threshold that leads to the kind of cascading failures Matthew was talking about.

MARGARET WARNER: And what about idea that Mayor Bloomberg said earlier, that also the power companies start shutting themselves down? Does that happen?

LAWRENCE MAKOVICH: Well, this interdependency is one in which the transmission lines and the generating stations themselves all have to operate in a highly coordinated fashion. So the analogy of a house of cards is not a bad one — that you have to rebuild this from the bottom up, and it requires some black start power plants to start up, to produce the power, that allows the bigger stations to start up.

They all have to be running synchronous each other in order to get the supply back on the grid, have that match the load that’s being reconnected. So it’s a process that takes an awful lot of coordination.

MARGARET WARNER: And I’m sorry. What is a black start power plant?

LAWRENCE MAKOVICH: It’s a plant that can start when there’s no power coming in from the outside. And so you need some of these reserve generators at big power plants to kick on to provide the power for the big power plants to get operating themselves.

MARGARET WARNER: Matthew Wald, what would you add to that in terms of the process that must be underway now to try to get this going again?

MATTHEW WALD: I was going to say this is a trick question. Many generating stations cannot make electricity unless they have electricity.

For example, I was at the Indian Point nuclear station this afternoon before the blackout; when the outside power goes down they have to shut down because they can’t operate without outside power. So you do have to put this together… I’m sorry. Are you still there? (sound problem)

MARGARET WARNER: Yes, we are. Go right ahead.

MATTHEW WALD: …Piece by piece. The other problem that you run into… I’m not sure that Con Ed actually shut itself down. (sound problem) I don’t know how much of this was its own volition and how much just happened to it.

MARGARET WARNER: Matthew, let me go back to Mr. Makovich for a minute and see if we can work that sound problem out.

What would you add to Mr. Makovich that in terms of the process that’s under way now? I mean how many of these black power stations are there? And are there enough to get the system up and running again?

LAWRENCE MAKOVICH: Well, yes, Matthew had mentioned back in ’64 I believe it was where we had the big cascading failure that also actually started in Canada. Since that time, the amount of coordination and planning and redundancy built into these networks has increased substantially.

So there are procedures in place to create this orderly rebuilding of the power system. It will take some time. What will probably take longer is the fault analysis, to really trace this back and understand what exactly has gone wrong.

MARGARET WARNER: Matthew Wald, back to you, if we can get you back.

MATTHEW WALD: Yes.

MARGARET WARNER: Go back to what caused this. Aren’t there usually some kind of warning signs that something like this is coming so that — I don’t know – a brown-out could be instituted or some way of anticipating this and prevent this go total cascade?

MATTHEW WALD: Yes. The fix is that the computers that run the system, or the human beings that run it, if they see an area of a problem, amputate it, drop load, so that supply and demand once again match.

The electric system is difficult because it’s instantaneous. The electricity is consumed at the very moment it’s produced. When you get out of what whack, you have to be vicious, you have to say, ‘I can’t run the whole system anymore, we’re going to chop off that part of it and let it go dark until we can get it running again.’

We can’t always get the system running again. You can always start at one end and rebuild it, but it’s complicated and can take some time.

MARGARET WARNER: You just raised the question of computer. How do they restart this when I’m sure a lot of the communication on this grid is by computer and now everyone’s computers are down?

MATTHEW WALD: Well, you know, since 9/11, they’ve done some strengthening to the system because the electric grid and the telecommunications network are very tightly interconnected — and those are two utilities that never liked each other very much — but since 9/11 they’ve worked together a little better and gone arm in arm.

There are live communications links even to power control centers that are down. And the power stations are pretty well hooked together, and they will start up on command. Some of them are remotely controlled. Some of them are controlled locally.

But they will start up on demand and they will synchronize with the grid so that all the electrons are sort of dancing in time, 60 cycles per second back and forth. And they will get it running. The reliability of the system really isn’t too bad if you think that it’s been since 1977 since the New York area had a major blackout. That’s a long time to go without a catastrophic failure for any system.

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